<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>尺寸</title>
    <style>
        .c1 {
            border: 1px solid red;
            height: 800px;
            max-width: 800px;
            min-width: 300px;
        }
    </style>



</head>

<body>
    <div class="c1">

    </div>
</body>

</html>